Formation of urea complexes with



June l5, 1954 E. GORIN FORMATION OF UREA COMPLEXES WITH COMPOUNDS, CONTAINING A MONOCYCLIC SUBSTITUENT Filed Sept. 13. 1949 2 Sheets-Shet l 'EPIRHT/FN W177i 0R WIT/M0 ,0 WasH/N6\ i l 23 ./zz

@ENTR/F065 zy il 2 Lifere 'ann/ INVENToR.

June l5, 1954 E, GORlN FORMATION OF UREA COMPLEXES WITH COMPOUNDS CONTAINING A MONOCYCLIC SUBSTITUENT Filed sept'. 13, 1949 2 Sheets-Sheet 2 SOLI/ENT (fl/4R65 ,emma/vim PLEXHND (z gggmfm (1-r/1mva-A/-dfmfm/NE) 'E e0 I A aman 52E# (nl .sf-'mm SETTLER .i9 V46 i5 55mm f4 IIE/: 6.9 arc/imam Ff. o3 A be/'d drz'n/ INVENToR.

BY 29m.;

Patented June 15, 1954 FORMATION F COMPOUNDS CONT CLIC SUBSTITUENT Everett Gorin, Castle Shannon, Pa., assignor to Socony-Vacuum Oil Company,

UREA COMPLEXES WITH AINING A MONOCY- Incorporated, a

corporation of New York Application September 13, 1949, Serial No. 116,593

The portion oi the term to June 16, 1970, h

6 Claims.

I. FIELD or' INvEN'IIoN Numerous processes have been developed for the separation of hydrocarbons and hydrocarbon derivatives of diierent molecular coniiguration by taking advantage of their selective solubility in selected reagents or solvents from which they may later be separated. Exemplary of hydrocarbon separation procedures is the Edeleanu process, wherein paraiiinic materials are separated from aromatics by virtue of the greater solubility of aromatics in liquid sulfur dioxide. Lubricant oil solvent refining processes, solvent deasphalting, solvent dewaxing and the like are further examples of the separation of hydrocarbons of diierent molecular configuration. Typical of selective solvent procedures for separating hydrocarbon derivatives is the separation of parafiin wax, monochlorwax and polychlor- Waxes, with acetone as the selective solvent.

This invention is concerned with the general eld outlined above, but based upon a different and little-known phenomenon, namely, the differing ability of hydrocarbons and hydrocarbon derivatives to enter into and to be removed from certain crystalline complexes. As used herein, the term complex broadly denotes a combination of two or more compounds.

, This invention is predicated upon the knowledge that urea forms complex crystalline compounds to a varying degreewith various forms of hydrocarbons and hydrocarbon derivatives.

II. PRIOR ART For some years it has been known that various isomers of aromatic hydrocarbon derivatives form complexes with urea. Kremann (Monatshefte f. Chemie `28, 1125 (1907)) observed that complexes, designated as double compounds, of urea and the isomeric cresols are stable at different temperatures. Schotte and Priewe (1,830,859) later separated meta-cresol from the corresponding para isomer by selectively forming a meta-cresol-urea complex. which was` described as an addition compound; the latter compound was separated from the para isomer and then split up by distillation or with water or acid to obtain pure meta-cresol. The addition compound of meta-cresci and urea was shown thereafter to have utility as a disinfectant (Priewe, 1,933,757). Bentley and Catlow (1,980,901) found a number of aromatic amines containing at least one basic amino group capable of forming double compounds with certain isomeric phenols. It has also been shown o1' the patent subsequent as been disclaimed that trans-oestradiol can be sepaarted from the corresponding cis-compound by forming a difficultly soluble compound of urea and. transoestradiol (Priewe, 2,300,134).

The forces between urea and the compounds of the foregoing complexes are due to speciiic chemical interaction between the various functional groups.

One heterocyclic compound, 2:6 lutidine, has been found to form a crystalline compound with urea, thus aiording a means of separating the lutidine from betaand gamma-picolines (Riethof, 2,295,606).

Comparatively few aliphatic hydrocarbon derivatives have been known to date to form complex compounds with urea. In German patent application B190,l97, IV Z/12 (Technical Oil Mission, Reel 143; Library of Congress, May 22, 194.6), Bengen described a method for the sep aration of aliphatic oxygen-containing compounds (acids, alcohols, aldehydes, esters and ketones) and of straight chain hydrocarbons of at least six carbon atoms from mixtures containing the same, the method being predicated upon the ability of such compounds and hydrocarbons to form Additions-Produkt with urea. In the Technical Oil Mission translation of the Bengen application, however, the urea complexes were designated adducts, which term apparently stems from the anglicized addition product.

III. DEFINITIONS From the foregoing discussion of prior art (II), it will be clear that a variety of terms have been applied to urea complexes. The latter have been rather loosely described as double compounds, addition compounds, difcultly soluble compounds, Additions-Produkt, and adducts All of these terms are somewhat ambiguous in that they have also been used to describe products o1' complexes of different character than the urea complexes under consideration. This is particularly so with the term adduct, and the related term unadducted materiaLn While the term adduct is simple and convenient, it is an unfortunate designation, inasmuch as it confuses these complexes with other substances known in the chemical art. Specically, adduct has been applied to Diele-Alder reaction products, formed by reaction of cnjugated diolens and olefins and their derivatives. As is well known, Diels- Alder products, as a rule do not revert to their original constituents when heated or treated with water, acids, solvents, etc. Moreover, the term adduct has been dened earlier as The product of a reaction between molecules, whichoccurs in such a way that the original molecules `or their residues have their long axes parallelto` to one another." (Concise Chemical and Technical Dictionary.)

3 Further ambiguity is introduced by the term adduction, which has been derlned as oxidation (Hackh.)

To avoid the foregoing conflicting terminology, l

several related terms have been coined to define with greater specificity the substances involved in the phenomenon under consideration. As contemplated herein and as used throughout the specification and appended claims, the following terms identify the phenomenon;

PleXad-a revertable associated complex comprising a plexor, such as urea, and at least one other compound; said plexad characterized by reverting or influence of heat and/or various solvents, to its original constituents, namely, a pleXor and at least one plexand.

PleXand-a compound capable of forming a plexad with a plexor, such as urea; compounds It has now been vdiscovered that certain terminally-substituted straight chain compounds, plexands, form plexads with urea. thas also been discovered that, by selective plexation with urea, a terminally-substituted straight chain compound can be separated, in the form of a plexad, from a mixture containing the same and a non-terminally-substituted compound. separation procedure is eifeotive also when the paraffin derivatives have the same number of carbon atoms, as in the case of isomers, or have a diiferent number of carbon atoms. Selective plexation is also effective when the terminal and non-terminal substituents are different, and the number of carbon atoms of the substituted parafns are the same or different.

The substituent groups which may characterize the terminally-substituted compounds are inorganic and organic groups of the following character thiazyl Cal-ENS, pyrazolyl Cal-13m, piperydyl CsHinN, etc; alkenyl methylene, vinyl, etc.; haloalkyl Vdichlormethyl C12CH-, etc.

decomposing, under the This.

As contemplated herein, the invention makesv possible the separation of one or more plexands from a Viniizture containing the same, such plexand or plexands being separated in the form of a pexad or piexads which, as described in detail hereinbelow, revert to the plexor, urea, and the plexand or pleXands under certain conditions. The separation, therefore, is an excellent means for obtaining, in pure or concentrated iorm, one or more pleXands or antiplexes whichever is the desired material. The invention also provides a means of forming new compositions of matter, namely, a number of plexads which may be used as a source of a plexor, urea, or as a source of a plexand.

V. OBJECTS this invention, therefore, to provide an effective means for separating hydrocarbons and hydrocarbon derivatives of different molecular configuration from mixtures containing the same.

t is also an object of this invention to selectively separate terminally-substituted straight chain compounds from midrturesV containing the same.

fr further object is to separate a terminallysubstituted straight chain compound from a mixture containing the same and a non-terminally substituted isomer. Y

Still another object is to separate a terminally'- substituted straight chain compound from a mixture containing the same and a non-terminallysubstituted straight chain compound having a different number of carbon atoms.

An additional object is to separate a terminally-substituted straight chain compound from a non-terminally-substituted compound, wherein the substituents are different and the number of It is an object of carbon atoms of the respective compounds arev Y the same.

A related object is to separate a terminally-substituted straight chain compound from a non-terminally-substituted compound, wherein the substituents are diierent and the number of carbon atoms of the respective compounds are different.

A further object is to separate a non-terminally substituted compound from a mixture containing the same and a second non-terminally substituted compound less susceptible to plexation.

Another important object is the provision of a continuous method of separation of said plexands and antiplexes, which method is flexible, capable of relatively sharp separation, and not highly demanding of attention and of utilities such as heat, refrigeration, pumping power, and the like.

An additional object is to provide a plexand or plexands substantially free of an antiplex or antiplexes. A corresponding object is the provision of an antiplex or antiplexes substantially free of said plexand or pleXa-nds.

Another object is to provide a new andnovel class or sub-classes of plexads comprising a plexn and and urea. A related object is the provision of a new and novel class or sub-classes of plexads comprising a secondary plexand and urea.

Other objects and advantages of the invention Vwill be apparent from the followingV description.

VI. INVENTON IN DETAIL Vwith urea (a plexor) of a plexand or plexands.

(l) PLEXANDS Plexands contemplated herein are represented by the general formula. (A)

wherein n is a whole number and wherein X is a substituent group of the character described above, with n and X being interrelated.

The substituent group X may be any of the types outlined above subject, however, to one important restriction, namely, that of geometrical size. Two dimensions are of importance in determining the nature of the separation that may be obtained between compounds-plexands and antiplexes-given above. The rst dimension is the cross-section of the group (X) taken in a direction perpendicular to the bond joining the group (X) to the parent hydrocarbon. This distancewidt "-is taken at the widest portion of the group and may be conveniently given a quantitative measure as the distance from betweenouter covalent radii of the two most widely separated atoms along the cross-section of the group where the covalent radii are those given by Pauling (Pauling-Nature of The Chemical Bond Cornell University Press; Ithaca, N. Y.: 1939). The second distance-lengthis the projection along the bond joining the group to the parent hydrocarbon of the distance from the center of the carbon atom to which the group is attached, to the center of the atom whose covalent radius shell extends furthest in the direction of said bond, plus the covalent radius of said bond.

The rst distance determines the length of the aliphatic chain required to obtain plexation at room temperature (25o C.) with a saturated urea solution, a plexor, when the group (X) in question is attached to the terminal carbon atom of the aliphatic chain. In the case of composite groups of the type GOY, -CI-IzCOY and -CH2Y, where Y is a non-aliphatic radical such as chlorine or amino, the =CO, -CHzCO and -CH2- constituents, respectively, are considered as part of the aliphatic chain and the width computed is that for the radical Y.

The widths of a number of typical groups computed according to the method given above are listed in order of size in Table I below:

TABLE I-w1D'rH or VARIOUS GROUPS 1N Al -CN 1.20 F 1.28 -Cl 1.98 -CHzCl 1.98 NH2 2.11 CONI-i2 2.11 -Br 2.28 -I 2.66 `SII 2.67

SO3H 3.69 Thienyl 4.38 Cyclohexyl 4.74 Phenyl 5.15 2 or 3 methyl cyclohexyl 5.49 `O- or M-tolyl 6.09

The correlation between the width of the group and the length of the aliphatic chain required for plexad formation at room temperature is an lapproximate one. This relationship depends to some extent upon the nature of the group (X) as well as upon the width of the group (X). For example, in the case where two groups (X) are the same size, the group 6. which imparts a higher` melting' point to the' substituted parain will form the stronger plexad, i. e., will form a plexad when the aliphatic chain is somewhat shorter in length.

Only the carbon atoms in the chain are considered to contribute to the chain length, that is, atoms such as oxygen, sulfur, nitrogen, etc., are not included in the atom total. Accordingly, then, the straight chain compounds contemplated herein include straight chain aliphatic hydrocarbons and straight chain aliphatic hydrocarbons in which one or more of the carbon atoms of the chain have been replaced by such atoms as oxygen, sulfur, nitrogen, and the like.

It is possible, however, to give the unequivocal limits for the relation between Width of the group (X) and size of the carbon chain required for plexation withurea at room temperature, 25 C. These limits are set forth in Table II below:

TABLE n.-coRRELATioN BETWEEN GROUPl UREA PLEXATON AT 25 C.

WIB TH O F .N'i'inirnum I u l h IChair; Jict Jeuot (510111) (in AU) Numberp Carbon Atoms It is to be understood that these limits apply y for plexation at temperatures of the order of about 25 C. The minimum number` of carbon atoms in the chain is generally lower for plexation at lower temperatures, but generally not more than one or two carbon atoms lower. In the same vein, for an increase in temperature, a correspondingly higher number of carbon atoms will be required in the carbon chain.

By way of illustration, the following compounds are typical plexands:

1 -nitro-n-decane; 1-nitro-n-dodecane;

1-nitro-n-octadecane; etc. amidon-octanamide; n-dodecanamide; n-octadecanamide; noctadecenamide; N methyl, n-octanamidei; N-hexyl, ndecanamide; etc. cyanate and isocyanate nhexyl cyanate; n-hexyl isocyanate; ndecyl cyanate; n-decy1 isocyanate; nhexadecyl cyanate; n-hexadecyl isocyanate; etc.

thiocyanate and isothiocyanate* n-decyl thiocyanate; n-decyl isotl'ii0 cyanate; n-octadecyl thiocyanate; n

octadecyl isothiocyanate; etc.

(X) AND MINIMUII CHAIN LENGTH FOR` 7, (c) sulfur-containing compounds:

Mercapton-octyl mercaptan; n-dodecyl mercaptan; n-hexadecyl mercaptan; n-octadecenyl mercaptan; etc.

sulfido (SR.)-

methyl, n-octyl sulfide; butyl, n-dodecyl sulde; amyl, n-hexadecyl sulfide; etc.

sulfaton-dodecyl sulfate; n-hexadecyl sulfate;

etc. sulfonyl haliden-decyl sulfonyl chloride; n-dodecyl sulfonyl bromide; n-hexade'cyl sulfonyl iodide; etc. (d) cyclic substituent:

1 cyclopropyl-n-octadecane; l-cyclohexyln-hexadecane; l-phenyl-n-'octadecanm 1- thienyl-n-octadecane; etc.

It is to be understood that terminally-substituted straight chain compounds containing a second terminal substituent on the opposite terminal carbon atom, are also contemplated herein as plexands. Such disubstituted compounds are also subject to approximately the foregoing relationships of terminal group widt and chain length. Compounds of this character are represented by the following formula:

wherein n, is a whole number, and X and X' are the same or diierent and as dened above.

Illustrative of such compounds are:

1,10-dichlor-n-decane; 1,8-n-octane diamine; 1,10-n-decane diamide; 1,12-n-dodecane dithiol; 1,18disulio-n-octadecane;V etc.

Another class of compounds contemplated herein as plexands are those having a non-terminal substituent, and being represented by general formula (B) wherein r and m are integers, the sum of which is equal to n-2, and 1L and X areas defined above.

The length, rather than the width, of the substituent group (X) roughly determines the minimum carbon chain length required for plexation of the foregoing plexands (B) namely, nonterminally substituted straight chain compounds. These compounds may be considered secondary plexands. The minimum chain length is also to some extent a function of the position substituted as well as of the chemical nature of the group. Thus, in compounds of this type, the minimum chain length required for plexation is determined by the length of group H3C(CH2) r-, if 1' is small enough so that this alkyl group is shorter in length than the substituent group (X). It is possible, bearing this relationship in mind however, also to give rather wide limits in the correlation of group length with the minimum chain length required for plexation. The lengths of Various groups are given in Table III, below, while the correlation of chain lengths with group lengths is given in Table IV, also provided below:

8 TABLE III -F 2.06 NH2 2.17 N02 2.61 5 -Cl 2.76 -SH 2.85 -Br 3.05 -CHzCl 3.11 -CN 3.25 l0 -SOal-l 3.37 -I 3.43 -Cyclohexyl (average configuration) 5.09 -Phenyl 5.69

TABLE IV.-CORRELATION BETWEEN LENGTH OF NONTE RMINALLY-SUBSTITUTED GROUPS AND MIN- IMUM CHAIN LENGTH REQUIRED FOR UREA PLEX- ATION AT C.

Minimum Chain Length, Number of Carbon i Atoms Group 7-l0 lll-13 13-18 lil-24 24 It is to be understood, once again, that the limits shown in Table IV apply for p-lexation at temperatures of about 25"V C. Here too, the minimum number of carbon atoms in the chain is somewhat lower for pier/:ation at lower temperatures, but generally not more than one or two carbon atoms lower. Also, a correspondingly highei` number' or" carbon atoms will be required in the chain for a rise in temperature.

Representative of the foregoing plexands are the following:

Considering the relationships shown by Tables III and IV, it will be seen that Z-chloro-n-octadecane, for example, will form a plexad with urea at about 25 C. This, then, illustrates a plexad comprising a secondary plexand and urea. A further illustration is a non-terminal bromide such as 2-bromo-n-tetracosane.

By way of illustration, it follows from the foregoing that l-bromo-n-tetracosane is separated readily from a mixture or the same and an isomer such as 2-bromo-n-tetracosane. This is typical of a separation of a compound represented by general formula (A) above, separated from a compound represented by general formula (B), above, wherein the halogen atoms and the number of carbon atoms thereof are the same.

A further illustration stemming from the foregoing data is the eicient separation of 1-chloron-octadecane from a mixture of the saine and V2- chloro-n-hexadecane; or a mixture ci the same and 2-chloro-n-cosane thus demonstrating the separation of a compound represented by general formula (A), above, irorn a compound represented by general formula (C):

wherein the sum of r-l-m is other than n-Z, and

substituents can be separated by plexation. This Y .halide represented feature is illustrated by selective plexad formation of 1chloronoctane in a mixture containing the latter and Z-bromo-n-octane. This may be referred to as the separation of a monohalide represented by general formula (A) from a monoby general formula (D):

naotonoronrcnomcna `wherein the sum of r-t'm is equal to n-2, and if wherein the sum orf r-i-m is other than n-z and e wherein the halogen atom X X in (A).

is dierent from (2) ANTIPLEX An antiplex, as defined above, is a compound incapable of forming a plexad with a plexor, such as urea.

(3) PLExoR The plexor used herein is urea, which is in solution in a singleor multiple-component solvent. This solution should range from partially saturated to supersaturated at the temperature at which it is contacted with a plexand or with a mixture containing one or more plexands and antiplexes, and, in many cases, it will be found convenient to suspend a further supply ci urea crystals in the solution, handling it as a slurry. For gravity or centrifugal separation, it is convenient to use a solvent of such a speciiic gravity that after the formation of a desired amount of plexad, the specific gravity of the solvent phase will be different from that of the plexad phase and of the antiplex phase to a degree sulicient to permit separation by gravity, centrifuging, etc.

The solvent should be substantially inert to the plexand and to the compounds of the mixture and also to the urea. Preferably, it should also be heat stable, both alone and in contact with urea, at temperatures at which the desired plexad is not heat stable.

As indicated above, the solvent may be either singleor multiple-component. It is sometimes convenient, particularly where the plexad is separated by gravity, to utilize a two-component system, as water and an alcohol, glycol,

vairline or diamine, and preferably a lower aliphatic alcohol such as methanol or ethanol, or a water-soluble amine such as piperidine. Such a solvent, partially saturated to supersaturated with urea, lends itself readily to a continuous process for separation by plexation.

Solutions containing sufficient water in order to minimize the solubility of the hydrocarbon derivatives in the urea solvent are often employed.

The minimum quantity of Water required in suchv instances depends upon the polarity and the molecular weight of the hydrocarbon derivative, or plexand, being treated and, in general, this .quantity will be greater with more polar plexands and with lower molecular weight compounds,

In certain cases the use of single-component solvents is advantageous. Single-component solvents other than alcohols may be employed, although they are normally not as useful as the lower aliphatic alcohols. Glycols may be employed as single solvents, yet ethylene glycol is generally not suitable in gravity separation operations due to the high density of the urea-saturated solvent. The higher glycols and particularly the butylene glycols may be advantageously employed. Diamines such as diamino-ethane, -propane and -butane may likewise be employed. Additional useful solvents include formic acid, acetic acid, formamide and acetonitrile, although the iirst three of these are subject to the same limitation as ethylene glycol.

Solvents generally useful when mixed with sufiicient water, ethylene glycol or ethylene diamine, to render them substantially insoluble in the derivatives being treated, are selected from the class of alcohols such as methanol, ethanol, propanol, etc.; ethers such as ethylene glycol dimethyl ether; and amines such as triethylamine, hexylamine, piperidine. When gravity separation is employed, the mixed solvent is preferably subject to the restriction that the density after saturation with urea must be less than 1.0-1.1.

( 4) TYPICAL SEPARATIONS In order that this invention may be more readily understood, typioal separations are.r described below with reference being made to the drawings attached hereto.

(a.) Separation of pleand from antz'plex The procedure which may be employed in effecting the separation of terminally-substituted from non-terminally substituted, straight chain hydrocarbons may be essentially the same as that described in copending application Serial Number 4,997, filed January 29, 1948. The plexand obtained in decomposing the plexad obtained in a urea. treatment of a mixture of terminally-subv stituted and non-terminally-substituted, straight chain hydrocarbons is very pure, provided the substituent group and the aliphatic chain length are of such dimensions that only the terminallysubstituted hydrocarbon forms a plexad and provided the plexad be carefully freed of occluded antiplex before it is decomposed. For example, substantially pure 1-halide is separated from the plexad obtained in the treatment of terminallysubstituted and non-terminally-substituted chlorides or bromides of normal parains containing from 8-16 carbon atoms.

In Figure l, a charge comprising a plexand and an antiplex, for example 1-bromo-n-octane and 2-bromo-n-octane, respectively, enters through line l, to be contacted with urea solution from line 2, and the charge and solution are intimately mixed in mixer 3. In case the charge undergoing treatment is rather viscous at the temperature of plexad (l-bromo-n-octane-urea) formation, it is advisable to provide a diluent, such as for example, a naphtha cut which may be recycled within the process, as described later, and joins the charge from line Il. Diluent make up is provided by line 5.

From mixer 3, wherein there is achieved an intimate mixture of urea solution and charge, the

`mixture iiows through line E, heat exchanger l,

Yferred to operate mixer 3 at a temperature somewhat above that conducive to heavy formation of piexad. Then, in heat exchanger l, the tempera.- ture of the mixture is reduced, and in cooler 8 adjusted, so that the desired plexad is formed. It wili be recognized that this showing is diagrammatic, and that the heat exchangers and coolers, heaters, etc., shown will be of any type suitable, as determined by the physical characteristics of the materials being handled.

From cooler B, the plexad-containing mixture ows into settler 9. This settler is preferably so managed that there is an upper phase of antiplex (Z-bromo-n-octane), an intermediate phase of urea solution, and a lower' region containing a slurry of plexad in the urea solution. The incoming mixtureV is preferably introduced into the solution phase, so that the antiplex (Z-bromo-noctane) may move upward and plexad downward, through some little distance in the solution, to permit adequate separation of plexad' from antiplex and antiplex from plexad.

Antiplex will be removed from settler t by line I and introduced into fractionator Ii, wherein the diluent is removed, to pass overhead by vapor line i2 and eventually to use through line 4. Recovered antiplex (2-bromo-n-octane) passes from the system through line I3. Obviously if no diluent be used, fractionator H will be dispensed with.

Plexad and urea solution, withdrawn from settler 9 through line i4, are passed through heat exchanger l and heater' I5 to enter settler it through line il. In this operation, t .e temperature is so adjusted that the plexand (l-bromo-noctane) is freed from the plexad and, in settler I6, the plexand rises to the top to be recovered from the system by means of line I8. The ure-a solution, thus reconstituted to its original condition by return to it of that portion of the urea which passed into plexad, is withdrawn from settler it by line E and returned to process. Naturally, in a process of this kind there are minor mechanical and entrainment losses of urea solution, etc., and urea solution makeup is provided for by line I9.

In many cases, the separation of plexad and solution from antiplex may be conducted with greater facility in a centrifuge operation. Such a setup is shown in Figure 2, wherein only the equivalent of that portion of Figure l centering about settler $3 is reproduced. Again in diagram form, the cooled mixture containing antiplex, plexad and urea solution enters centrifuge Zt through line In many cases, it will be desirable to utilize a carrier liquid in known manner in this operation and that liquid may be introduced by line 2|. Antiplex will be carried oil through line le, and plexad, urea solution, and carrier, if present, pass through line 22 to a separation step, which may include 'washing and may be carried out in a settler, a filter, or Vanother centrifugal operation, which separation is indicated diagrammatically at 23. Carrier liquid, if used, returns through line 2li, and urea solution and plexad pass through line i4. (Note: Lines il! and iii are the same lines, for the same functions, as in Figure l and are identically numbered.)

(b) VS'epcratic1t of one plezcand from ct second plexand sharpness of separation of the terminally-substituted compound will be greater, the greater the difference inthe strength of the plexads formed with the two types of pure compounds- In general, this will be greater, the shorter the carbon chain length of parent hydrocarbon. For example, substantially pure l-bromo-n-octane can be obtained from a mixture with 2-bromo-noctane in a single plexation. It is more difficult, however, to obtain separation between l-chloron-octadecane and 2-chloro-n-octadecane.

The following serves to illustrate a procedure Y for obtaining sharp separation between one plexand, l-chloro-n-octadecane, and a second plexand, 2-chloro-n-octadecane, the latter behaving as a secondary plexand in forming a plexad. 'I'his procedure is similar to a sweating or a solvent sweating procedure used in the reiining of slack waxes, and is shown diagrammatically in Figure 3.

In Figure 3, a slurry of solid urea in a saturated urea solvent, which is preferably an aqueous alcoholic solution, is pumped from line 3i into a turbo mixer 32 where it is agitated With a mixture of 1- and 2-chloro-n-octadecanes, which enter through line 33. An immiscible solvent charged through line 36 is also preferably employed, such as a light cut from a straight run naphtha .in case the compounds of the mixture treated have: (l) a relatively high viscosity; (2) an appreciable solubility in the urea solvent; or (3) greater density than the urea solvent. The amount of excess solid urea employed should be sufficient so that after the plexation is completed the urea solvent remains substantially saturated with urea.

Internal cooling means may be employed in 32 to further cool the mixture and remove the heat evolved during the plexation. The tem'- perature employed in 32 will depend upon the chain length of the plexand and secondary plexand. If the chain length is such that it is not more than one or two carbon atoms greater than the minimum required to obtain plexation with the pure plexand at 25 C., then temperatures in the range of to 20 C. should be employed. If the chain length is from two to six carbon atoms greater than the minimum, ternperature in the range of -30 C. should be employed; and if the chain length is greater than six carbon atoms beyond the minimum, temperatures from -50" C. may be employed. It will be apparent, then, that conditions of operation vary considerably, conditions selected being those appropriate for the formation of the desired plexad or plexads.

The slurry of plexad, urea solvent and secondary plexand is pumped, by means of pump 36, through line and cooler 3l wherein it may be further cooled if desired, and into gravity settler 38. In settler 38 the secondary plexand plus naphtha solvent rises to the top and is withdrawn through line 39 into fractionator di). rIhe secondary plexand, predominantly 2-chloro-n-octadecane, is removed as bottoms from fractionator 40 through line 4 i. The naphtha solvent is taken from fractionator 4l! through line 42, cooler 43, tank 44 and line 45 to be employed in solvent sweating zone 4t. Naphtha solvent may also be recycled to fractionator 4D through line 4l, by means of pump 48.

In settler 38, the slurry of plexad in urea solvent is taken off through line 49, heat exchanger and heater 5| into solvent sweating zone (or mixer) 46. A portion of the clear urea solvent `may be removed from if desired.

the centerof 33 and re- PLEXATION AT I4 mum chain length required for plexation found experimentally is compared with the correlations given in Table IV. Table V is as follows:

MINIMUM FOP CHAIN LENGTHS REQUIRED FOR UREA EYDROCARBONS-l DETE RMINED EXPERI- MENTALLY WITH THOS'E GIVEN IN TABLE II.-PLEXAD FORMATION-ALI- PHATIC CHAIN LENGTH Minimum Group Chain Length No. Correlation,

Table II It is to be understood that the gravity settler 38 may be replaced by other separation means such as a centrifuge or rotary lter, etc.

. The mixture of solvent and plexad is heated insolvent sweating zone 46 to a temperature suicient to decompose the major portion of the plexad of the Z-chloro-n-octadecane, while prer serving the major portion of the plexad of l-chloro-n-octadecane. The temperature em ployed in zone d6` is related to that employed in mixer 32, and will generally be maintained from -20" C..higher in zone 46 than in mixer 32.

The partially decomposed plexads, urea solvent, and naphtha mixture is passed from zone 46 through line 53 to settler 54. The naphtha containing plexand, l-chloro-n-octadecane, and some secondary plexand, 2-chloron-octadecane, is recycled through lines 55 and 33 to mixer 32. The slurry of undecomposed plexad is withdrawn from the bottom of settler 54 through line 56, heat exchanger 5l, heater 58 into settler 59. The plexad is thus heated hot enough to cause complete decomposition or reversion of the plexads and solution of the urea `in the urea solvent. Temperatures in the range of 55-85 C. are generally suitable. i

Plexand, 1chloronoctadecane, contaminated with naphtha which had been occluded on the corresponding plexad (1-chloro-n-octadecaneurea) is withdrawn through line 6l) into fractionator 6i. Naphtha is taken off overhead from fractionator 6! through line 62, cooler 63, tank 64, pump 65 and line 66, to mixer 3l. A portion of the naphtha may also be recycled to fractionator 6l through line 61. Plexand is recovered as bottoms through line 68.

Urea solution is recycled from the bottom of settler 59 through line 69, pump 10, heat exchangers 57, and 50, and line 5I. A

Plexand of any desired purity may be obtained by either: (1) increasing the fraction of the total plexad decomposed in the solvent sweating zone (46), or (2) including a multiplicity of alternating solvent sweating zones (46) and settling zones (54) operated in series.

VII. ILLUSIRAIIVE EXAMPLES The following examples serve to illustrate, and not in any sense limit, the present invention.

(a) Terminally-substituted straight chain pamins, general formula A A number of such paralin derivatives of varying chain length were agitated for several hours It will be noted from the data set forth in Table V that, in all instances, experimental values found for the minimum chain length are within the limits specified in Table II. For example, it will be observed that a typical straight chain compound containing a cyclic substituent, stearoyl thiophene, forms a plexad.

(b) Comparison of equilibrium 'values in the pleation of compounds of general formula (A) and (B) Plexation of a plexand, dissolved in an antiplex such as a suitable branched chain hydrocarbon solvent, with a saturated urea solution proceeds until the concentration of the plexand is reduced to a certain minimum concentration which may be termed the equilibrium concentration. In

general, the equilibrium concentration is lower, the lower the temperature of plexation and is dependent only upon the temperature and not upon the solvent for the plexand, provided the urea solution is maintained saturated with urea land provided the pleXand-solvent phase can be regarded as an ideal solution.

Equilibrium values were determined for several pairs of compounds, (A) and (B), by agitating D solutions of Varying concentrations of the substituted hydrocarbon in methanol-30 water solution saturated with urea and noting the minimum concentration required for plexad formation. The results are suln marized in Table VI, below.

TABLE VI.-EQUILIBRIUM VALUES IN THE UREA ll'ATION OF HYDROCARBONJ, HYDROCARBON-Z iso-octane With a No Plexad.;

From the data shown in Table VI, it will be noted that the terminally-substituted compound, (A), forms a plexad, while the non-terminallysubstituted compounds, (B), do not form plexads. When the compound (B) does not form a plexad, relatively sharp separation can be obtained between compounds (A) and (B) in a single plexation.

` (c) Separation of 1-bromo-n-octane `and 2-bromo-ri-octa'ne` The following solution was contacted with urea,

enen-3.34

. 15 in a reaction vessel: equal parts by volume of 1-bromo-n-octane, 2-bromo-n-octane and 2- methyl pentane. A portion, 45 parts by volume, of this solution was agitated at room temperature (25 C.) with 50 parts by volume of an aqueous 89% methanol solution saturated with urea at 45 C. A plexad was formed and settled to the bottom of the urea solution. The upper layer, free of plexad, was decanted from the lower layer.

The upper layer was distilled whereupon 2-methyl From the foregoing description, it will 'be apparent that the invention lhas considerable application in the chemical and related arts. For example, terminally sulonated paraflins may be separated from the non-terminally substituted compounds in the manufacture of detergents and wetting agents by the suloecl'lloiination of paralins. This makes possible purer and more eiicient detergents and wetting agents. Similarly, l-chloro straight chain paralins may be separated from the corresponding non-terminally substituted chloro compounds, which are formed in the chlorination of straight chain paraflins. Also, in the high temperature, vapor-phase chlorination of olens, two principal products are produced, namely, the l-chloro2eoleiin and the 3-chloro-1-olein according to the .followingr representation:

The present method may be employed to effect the separation between the foregoing l-chloro and the S-chloro compounds.

The addition of a mercaptan or hydrogen bromide to a l-olen in the presence of air, oxygen or peroxides takes place with the addition of the mercaptoradical, -'SR, or bromo radical, -Br,

to the terminal carbon atom of the oien. f an oleiin mixture containing a straight chain 1- olelin is so treated, the derivatives obtained from the straight chain 1-olehn can be selectively such an undesirable constituent are present.

In addition, the new plexads made available herein constitute desirable sources of urea and of the various plexands associated therewith. For example, the desired compounds can be kept in storage or shipped until just prior to use, when Vthey vare separated by reversion of the plexads.

continuation-in-part said 4,997 iiled This application is a co-pending application Serial Number January 29, 1948.

Halogen compounds can be plexated fromV mixtures containing the same form urea plexads, as described above and as described and claimed in application Serial No. 115,511, now abandoned. Compounds characterized by a nitrogen-containing substituent are also plexated from mixtures containing the same Vand form plexads with urea, asdescribedabove; this subject matter is also described and is claimed in application Serial No. 115,515. Sulfur-containing compounds are also plexated from their mixtures, and form plexads with urea, as described above and as described and claimed in application Serial No. 255,943, iiled November 13, 1951, as a continuation of application Serial No..115,516 which has been abandoned. Plexation with urea of various terminally substituted compounds from mixtures containing the same and non-terminally substituted compounds, described above, is also described and is claimed in application Serial No. 115,517.

Urea plexation of a non-terminally mono-substituted compound from mixtures containing the same and a non-terminally poly-substituted compound is described and is claimed in application Serial No. 115,513now U. Si. Patent No. 2,642,422. Urea plexation of mixtures containing aliphatic compounds of different degrees of unsaturation is described and is claimed in application Serial No. 115,514; similarly, plexation of mixtures containing aliphatic hydrocarbons o diilerent degrees of unsaturation and urea plexads of such hydrocarbons, are described and are claimed in application Serial No. 115,518, now U. S. Patent No. 2,642,423, and in divisional application thereof Serial No. 266,547, led January 15, 1952.

Said applications Serial Nos. .115,511 and 115,513 through 115,518 were filed concurrently with this application on September 13, 1949.

Application Serial No. 374,707, filed August 17, 1953, is a continuation of said abandoned application SerialV No. 115,511.

Application Serial No. 407,197, filed February 1, 1954, is a division oi application Serial No. 115,515, filed September 13, 1949.

Application Serial No. 410,573, led February 16, 1954, is a division of application Serial No. 266,547, filed January 15, 1952, which, in turn, is a division of said lapplication Serial No. 115,518 (now Patent No. 2,642,423).

I claim: v

1. The method of separating a compound represented by general formula (A) t wherein X is a monocyclic group, and 1L is a whole number greater than about: 8 to 10 when the "width of X is between about 3.0 A" and about 3.7 A", 10 to 16 when the width of'X is between about 3.7 A and about 5.2 A", and 16 when the width of X is greater than about 5.2 A", from a mixture containing the same and an isomer thereof represented by general formula (B) wherein X is an identical monocyclic group, and 7 and m are integers Vthe sum of which is equal to 11-2, which comprises: contacting said lmixture with urea under conditions appropriate for the formation of a crystalline complex of urea and said compound (A); and. separating said complex from said mixture.

2. Crystalline complex of urea and a compound represented by the general formula wherein X is a monocyclic group and n is a whole number greater than about: 8 to 10 When the width of X is between about 3.0 A and about 3.7 A", 10 to 16 when the width of X is between about 3.7 Au and about 5.2 A", and 16 when the width of X is greater than about 5.2 A".

3. Crystalline complex of urea and a compound represented by the general formula wherein X is a monocylic group, and r and. m are integers the sum of which is greater than about twenty-one carbon atoms.

4. Crystalline complex of urea and stearoyl thiophene.

5. Crystalline complex of urea and a compound represented by the general formula wherein X is a monocyclic heterocylic group and n is a whole number greater than about: 8 to 10 when the width of X is between about 3.0 A and about 3.7 A", 10 to 16 when the width of X is between about 3.7 A and about 5.2 A, and 16 when the width of X is greater than about 5.2 A".

6. Crystalline complex or" urea and a compound selected from the group consisting of:

(1) X(CII2)CH3 wherein X is a monooyclic group and 1L is a whole 18 number greater than about: 8 to 10 when the width of X is between about 3.0 A" and about 3.7 A", 10 to 16 when the width of X is between about 3.7 A and about 5.2 A", and 1 6 when the widt of X is greater than about 5.2 A", and. (2) HQCHQAIUHwHQmOHS wherein X is a monocyclic group, and r and m are integers the sum of which is greater than about twenty-one carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Bengen-Reel 143 T. O. M. deposited in Library of Congress May 22, 1946, pages to 139.

Powell, Chem. Soc. Jour., 1948, Part 1, pages 61-73.

Schlenk, Jr., Angew. Chem., 61 Jahrg. 1949/Nr 11, page 447. 

6. CRYSTALLINE COMPLEX OF UREA AND A COMPOUND SELECTED FROM THE GROUP CONSISTING OF: @SP X(CH2)NCH3 @SP WHEREIN X IS A MONOCYCLIC GROUP AND N IS A WHOLE NUMBER GREATER THAN ABOUT: 8 TO 10 WHEN THE "WIDTH" OF X IS BETWEEN ABOUT 3.0 A* AND ABOUT 3.7 A*, 10 TO 16 WHEN THE "WIDTH" OF X IS BETWEEN ABOUT 3.7 A* AND ABOUT 5.2 A*, AND 16 WHEN THE "WIDTH" OF X IS GREATER THAN ABOUT 5.2 A*, AND 